Sensors comprising a waveguide composed of a core and a clad each made from an elastomeric material are known. Such a sensor may include light emitting means and light receiving means each connected to ends of the optical waveguide. The core or clad, or both, may be transparent, and the core has a refractive index somewhat larger than that of the clad. Both core and clad may be made from a synthetic rubber or gel.
Compositions used in preparing waveguides have been disclosed, for example in U.S. Pat. No. 4,529,789. However, this composition cures to form a gel having inadequate refractive index and insufficient impact resistance for some applications. The resin present in this composition may also cause cloudiness, which is undesirable for optical waveguide applications.
Existing waveguides are frequently prepared by first fabricating a core and thereafter coating the core with a clad material. Such methods include extruding a high viscosity transparent composition through a nozzle, curing the composition to form the core, applying a liquid clad material to the outer periphery of the core, and thereafter curing the clad material. Sensors made from such waveguides suffer from the drawback that additional connectors are required to attach parts of the sensor, such as radiation sources and detectors at the ends of the waveguide. This adds process steps and cost to fabricating the sensor.